It has been long known that a carrier wave may be modulated by an information-bearing signal in order to transmit that signal along the carrier wave. Typically, in data transmission as well as voice transmission in telephone applications, the carrier signal is carried on copper wires in the form of electrical current. It is also known that improved results may be achieved by replacing the electrical components with optical components and modulating an optical signal along a waveguide or other optical components.
Prior art optical techniques for modulating signals may take the form of a mechanical shutter which is interposed between areas of light transmission. These shutters tend to be slow, and would not be efficient in transmitting data at high rates of speed. Another technique includes the use of an optical crystal across which electrical voltage may be applied. Light from a laser is injected into one side of the crystal and a light-receiving means such as a waveguide would receive the light passing through the crystal from the laser. Voltage applied across the crystal alters the optical characteristics of the crystal to change or modulate the light passing therethrough. This provides a workable optical modulation device. However, it can be seen that the components used to form such modulation device, namely a laser and an optical crystal, are quite expensive. Also the voltage which must be applied across the crystal must be in the range of 10 KV or greater. Thus, known optical modulating devices cannot be easily or inexpensively constructed. Therefore, it is desirable to provide an optical fiber modulations assembly which may be composed of relatively inexpensive components yet provide the desired modulating characteristics. The modulation assembly could be interposed between a pair of transmitting fibers to modulate the light therebetween.